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Full text of "The manufacture and properties of iron and steel"

THE BLAST FUENACE.
77
unburned combustible as well as from the sensible heat carried away by the inert steam in the products of combustion
SEC. Hi.—Seating the bfcw*.—The energy present in the tunnel head gases is used for two purposes: (1) heating the blast: (2) producing power. It has been shown in the foregoing calculations that a normal furnace, using from 1800 to 2300 pounds of coke per ton of iron, requires from 115,000 to 125,000 cubic feet of air per ton of coke burned, the exact volume depending on the carbon ratio and other working conditions. Assuming 120,000 cubic feet-as a basis and that the air is heated to 1100° F., at which temperature its specific heat is .022 B.t.u. per cu. ft., the blast for one ton of coke will require
120,000X0.022X1100=2,904,000 B.t.u.
Assuming that the hot stoves give an efficiency of 50 per cent., the energy in the gas sent to these stoves must amount to 5,808*000 B.t.u. for each ton of coke burned. The total energy contained in the tunnel head gases under usual conditions amounts to about 16,000,000 B.t.u. per ton of coke burned, so that under the above assumptions the stoves require a little over one-third of all the gas. This agrees with the estimates usually made by furnacemen. SEC. Us.—Combustion of the gas under I oilers.—The composition of tunnel head gas varies widely, but the composition of the products of combustion obtained by burning different gases is practically the same without regard to these variations. * Taking C in Table II-F as a normal gas and A and 0 as extreme cases, the gases resulting from their perfect combustion will be as shown in Table II-G, when just the amount of air is used that is theoretically necessary:
TABLE II-G.
Products of Combustion of Tunnel Head Gas.
Composition of ga,s : by volume.						Composition of products of conibustion : by volume.	
	C02	CO	'H	0	N	C02	N
0 A O	11.97 16.93 6.67	26.43 21.22 33.33	1.50 1.50 1.50	0.30 0.30 0.30	• 59.81 60.05 58.20	25.64 27.05 24.58	74.36 72.95 75.42